System and method for implementing a robot proof web site

ABSTRACT

The invention prevents robots from browsing a Web site beyond a welcome page. When an initial request from an undefined originator is received, the Web site responds to it with a welcome page including a challenge. Then, on receiving a further request from the undefined originator, the Web site can check whether the challenge is fulfilled or not. If fulfilled, the undefined originator is assumed to be a human being and authorized to go on. If the challenge is not fulfilled, the undefined originator is assumed to be a robot, in which case site access is further denied. 
     The invention prevents Web site contents from being investigated by robots while not requiring users to have to log on.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/113,607, filed on May 1, 2008, now allowed, which is a Continuationof U.S. patent application Ser. No. 09/901,442, filed on Jul. 9, 2001,now U.S. Pat. No. 7,373,510, which claims priority to European PatentApplication 00480085.0, filed Sep. 12, 2000, which are all incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to the Internet and more particularlyapplies to those of the World Wide Web (WWW) sites that, while welcominghuman beings, want to exclude robots from visiting and gatheringinformation from them.

BACKGROUND OF THE INVENTION

WWW robots, also called Web Wanderers, Web Crawlers or Web Spiders, andoften just referred to as bots (bot is short for robot), are programsdevised to automatically traverse the hypertext structure of the Web.Such bots, having retrieved a document, can also recursively retrieveall the linked pages referenced in the document. This is especially thecase of numerous search engines and their robots which roam the WorldWide Web finding and indexing content to add to their databases.Although most robots provide a valuable service, concern has developedamongst Web site administrators about exactly how much of their preciousserver time and bandwidth is being used to service requests from theseengines.

While the majority of robots are well designed, are professionallyoperated and cause no problems, there are occasions where robotsvisiting Web servers are not welcome because of the way robots behave.Some may swamp servers with rapid-fire requests, or retrieve the samefiles repeatedly. If done intentionally this is a form of Denial ofService (DoS) attack, although this is more often just the result of apoor or defective robot design. In other situations robots traverseparts of WWW servers that are not suitable for being searched e.g.,contain duplicated or temporary information, include large documents ore.g., CGI scripts (CGI is a standard for running external programs froma World-Wide Web HTTP server). In this latter case and in similarsituations, when accessed and executed, scripts tend to consumesignificant server resources in generating dynamic pages and thus, slowdown the system.

In recognition of these problems many Web robots offer facilities forWeb site administrators and content providers to limit what the robot isallowed to do. Two mechanisms are provided. One is referred to as the‘Robots Exclusion Protocol’, even though it is not really an enforcedprotocol, but was a working draft document discussed as anInternet-Draft by the Internet Engineering Task Force (IETF) in 1996under the title ‘A Method for Web Robots Control’. According to thisdocument, a Web site administrator can indicate which parts of the siteshould not be visited by a robot. This is accomplished by providing aspecially formatted file, in http:// . . . /robots.txt. The secondmechanism assumes that a Web author can indicate whether a page may ormay not be indexed, or analyzed for links, through the use of a specialHyper Text Markup Language (HTML) META tag i.e., a ‘Robots META tag’.However, both of these mechanisms rely on cooperation from the robots,and are not even guaranteed to work for every robot. Moreover, asalready suggested here above relative to Dos attacks, some of theserobots may not be so friendly. They could be run e.g., with themalicious intent of attacking a Web site (then, they just ignore therobots.txt file and the robots meta tags) so the site becomes overloadedand starts refusing to serve legitimate users i.e., the human beingstrying to make normal use of the site.

Also, although the information made available on a site may not beconfidential, an administrator may want to prevent the unlimiteddissemination of it that would otherwise result from the indexing andreferencing activities of all sorts of robots. The standard way ofachieving this is to protect a Web site through some form ofauthentication, of which the more common method is to manage a list ofregistered users having a password so as they have to sign on uponaccessing the site. The obvious drawback of this is that administratorsmust manage and update a closed list of users. This requires aregistration step for a first consultation of a site and also assumesthat users will remember their passwords in subsequent consultations.This may not be at all what the administrator wanted to achieve, and mayeven be counterproductive, since it will certainly discourage someindividuals who are willing to browse a site to go further if they arerequested to register.

Object of the Invention

Thus it is a broad object of the invention to prevent Web site contentsfrom being investigated by robots.

It is a further object of the invention to encourage human beings,attempting to access a robot protected Web site to proceed further bynot imposing a registration at first access and a log on procedure ateach subsequent access.

It is still another object of the invention to avoid reliance on arobot's cooperation for barring the robot's access to contents of Websites.

Further objects, features and advantages of the present invention willbecome apparent to the ones skilled in the art upon examination of thefollowing description in reference to the accompanying drawings. It isintended that any additional advantages be incorporated herein.

SUMMARY OF THE INVENTION

A method and a system for preventing robots from browsing a Web sitebeyond a welcome page are described. On receiving an initial requestfrom an undefined originator the Web site responds to the request with awelcome page including a challenge. Then, on receiving a further requestfrom the undefined originator, the Web site can check whether thechallenge is fulfilled or not. If fulfilled, the undefined originator isassumed to be a human being and the site keeps request and allsubsequent ones, if any. However, if the challenge is not fulfilled, theundefined originator is assumed to be a robot, in which case allrequests from that originator are not further processed.

The invention prevents Web site contents from being investigated byrobots without requiring end users to register or the site administratorto have to manage an access list of authorized users.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary welcome page per the invention.

FIG. 2 shows the corresponding HTML code.

FIG. 3 shows the steps of the method of the invention.

FIG. 4 shows the further steps of the method when access to a Web siteper the invention is denied, while a timer is on, for requests carryinga logged IP address.

FIGS. 5A and 5B are other exemplary welcome pages with challenges.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates the method according to the invention to prohibitrobots from accessing a Web site beyond its welcome page. An exemplarywelcome page as seen by an individual accessing a Web site e.g., atfollowing URL [100] (Uniform Resource Locator)‘http://www.anysite.com/welcome.html’ is shown. Accessing a Web site canbe done with any available Web browser e.g., Netscape browser [110] fromNetscape Communications Corporation, 501 E. Middlefield Road, MountainView, Calif. 94043, USA can be used. Then, according to a first methodto prohibit robot's access, the welcome page implements a dummychallenge that can be simply answered by a human being, but which arobot should certainly fail.

Among various possibilities, FIG. 1 illustrates a typical challengeaccording to the invention. The welcome page thus shows an image [120]including, in this particular example, a few geometric forms that can beunambiguously referred to by a single word or expression in a languagethat the individual accessing the Web is assumed to be capable ofreading. Then, associated with the image which, as depicted here,includes a square, a circle, a cross and a triangle, the reader isprompted [130] to click e.g., on the cross [121]. A human being,desiring to go on and visit the site, will do it naturally while a robotwill do nothing, or will do it wrongly simply because it just does notunderstand the graphic symbols or which of them may be a cross. Hence,this invention easily allows discrimination of a human being from arobot on the basis of their respective levels of abstract reasoning,which is naturally high, or very high, for a human being while a robotis totally lacking this capacity. This allows achievement of theobjectives of the invention to prevent robots from browsing the sitebeyond the welcome page, while neither imposing to the people accessingit the burden of having to register and to log on, nor requiring theadministrators of the site to manage a list of legitimate users.

To make the site even more resistant to browsing by a “smart” robot thatcould be tailored to adapt to a given challenge or set of predictablesuch challenges, prompting can be made random so that every time someoneaccesses the site, the challenge is different. For example, the crosscan be moved to a different position on the image map so that thecoordinates returned, when clicking on it, are different. Or, theprompting request can change in requesting e.g., to click on triangleinstead.

FIG. 2 shows the source HTML (Hyper Text Markup Language) code [140] forthis example which uses a server side map i.e., ismap [142], included inan anchor tag created with the <a . . . > . . . </a> construct form[149] of the HTML language. Thus, when the user clicks on the cross[121], the browser sends a request back to the server URL(/cgi-bin/challenge.exe) [141] including the X and Y coordinates of theuser's click contained in an ismap [142] so that the server can checkwhether the click coordinates indeed match the cross position. Theanchor tag also carries an identification field i.e., id=XD34F739 [143]which is useful to correlate the answer, including the clickcoordinates, with the current challenge when this latter changes fromone user to another as explained above.

FIG. 3 depicts the steps of the method according to the invention whenan originator of an initial request to access a Web site is responded towith a challenge. Upon receiving this initial request, the [300] Website server responds with the challenge [310]. This is done through theestablishment of a TCP connection with the originator (the reliabletransport protocol of the Internet TCP/IP suite of protocols used by theWeb). The response is in the form of a Web page including a challengee.g., of the kind discussed in FIG. 1. Then, having gotten the server'sresponse, the originator proceeds with a new transaction containing hisclick response directed towards the Web site [320]. On receiving the newtransaction, the Web site server checks whether the challenge isfulfilled or not [330]. If the response matches the challenge prompt[340], then the site server assumes that the originator is a human beingand permits further access. However, if the Web server finds thatchallenge is not properly answered, it must assume that the originatoris a robot [350]. As a consequence, it stops processing all current andfurther requests, if any [351], which includes dropping the TCPconnection or redirecting it to another site [352]. Also, the IP sourceaddress [361] may be remembered and a timer started [362] so that accessto the site may be temporarily barred, from that IP source address, asexplained in FIG. 4.

FIG. 4 shows the case where the IP address of an assumed robotoriginator is remembered. Then, the server may be implemented totemporarily drop or redirect immediately all requests issued with thisparticular source IP address, because all subsequent access requeststhereafter are assumed to come from a robot (although this might notalways be true since a robot may be behind a proxy or firewallperforming a network address translation of all the IP source addressesit has to forward). Because the IP source address of the request waslogged and a timer started as explained in FIG. 3, each time a newrequest is received [410] the server first checks for whether the samelogged source IP address is found [420]. If not the same address, accessmay proceed normally [450]. If the address is the same, however, a timeris checked [430]. If the timer interval has elapsed, the logged IPaddress is reset [440] and new request is normally handled [450], i.e. anew challenge is issued. However, if timer has not elapsed, the TCPconnection is dropped or redirected [460] before the server resumeshandling of newly received requests [410].

FIGS. 5A and 5B illustrate other exemplary challenge examples that areeasily answered by human beings.

FIG. 5A takes the form of a quiz [510] which could be made as simple asshown [500] or as sophisticated as necessary to defeat elaborated or“smart” robots or, alternatively, to adapt to a particular end-userpopulation sharing a common type of skill.

FIG. 5B is another alternative that combines images [520] and text [530]in an even more abstract way where the answer is suggested by the text,so it is even better adapted to discriminate a human being from a robot.However, it is worth mentioning here that such a challenge isculture-dependent and could serve as well to discriminate human beingson the basis of their social or ethnic origins.

What is claimed is:
 1. A system for preventing robots from browsing aWeb site beyond a welcome page, comprising: a computer having at leastone processor and a memory, the computer comprising program code thatwhen executed by the at least one processor causes the computer to:receive an initial request, directed to the Web site, from an undefinedoriginator; respond to the initial request with a challenge that promptsa response to the challenge from the undefined originator; and receivethe response to the challenge from the undefined originator, wherein thechallenge includes: a plurality of graphical forms, and an accompanyingtextual expression describing one of the plurality of graphical forms,and the response to the challenge includes an identification of alocation of the described one of the plurality of graphical forms. 2.The system of claim 1, wherein the computer further comprises programcode that when executed by the at least one processor causes thecomputer to modify the challenge in response to a second initialrequest.
 3. The system of claim 2, the program code to modify thechallenge in response to the second initial request comprises programcode to vary a coordinate location of the described one of the pluralityof graphical forms.
 4. The system of claim 2, wherein the program codeto modify the challenge in response to the second initial requestcomprises program code to vary which one of the plurality of graphicalforms that is described by the accompanying textual expression.
 5. Thesystem of claim 1, wherein the computer further comprises program codethat when executed by the at least one processor causes the computer toprocess further requests from the undefined originator after thechallenge has been successfully fulfilled.
 6. The system of claim 1,wherein the computer further comprises program code that when executedby the at least one processor causes the computer to stop processingfurther requests from the undefined originator after the challenge hasnot been successfully fulfilled.
 7. The system of claim 6, wherein theprogram code to stop processing further requests from the undefinedoriginator after the challenge has not been successfully fulfilledcomprises program code to drop or redirect a TCP connection establishedwith the undefined originator.
 8. The system of claim 1, wherein thecomputer further comprises program code that when executed by the atleast one processor causes the computer to log a source IP address ofthe undefined originator, and to start a timer.
 9. The system of claim1, wherein the computer further comprises program code that whenexecuted by the at least one processor causes the computer to: receive anew request; determine whether a source IP address of the new requestmatches the logged source IP address of the undefined originator;determine whether said timer is expired; and upon the source IP addressof the new request matching the logged source IP address of theundefined originator and the timer being expired, respond to the newrequest with a second challenge that prompts a response to the secondchallenge.
 10. The system of claim 1, wherein the location of thedescribed one of the plurality of graphical forms is X and Y coordinatesof the undefined originator's click associated with the challenge.